Perforated blocks of the stated type are known, for example, as shown in German Gebrauchsmuster (German Utility Model) 72 45 452 and German patent DE-37 19 245 A1. By means of the holes of the perforated blocks, rainwater can drain off in advantageous fashion without pools and undesired water surfaces forming. Above all, however, the rainwater is to seep into the subsoil and be led to the groundwater instead of flowing into the sewerage. An important point is that the size of the holes must not be so large that problems arise in walking on the surfaces. For example, heels of ladies' shoes must not get caught in the holes. For this reason, the holes should have a diameter of approximately 5 to 20 mm. Perforated blocks of this type must not be confused with blocks that have large openings into which earth is poured (lawn checker bricks and so forth) so that the surfaces will be greened.
Initially, it was attempted to lay such perforated blocks without jointing or sanding-in the blocks, in order to prevent the holes being filled with sand during jointing so as to threaten the drainage of water. This has, however, proved unfavorable because the blocks are not firmly enough supported one against another and the perforated blocks do not sit solidly enough when the surfaces are under load, for example when the surfaces are walked on.